iommu/core: let drivers know if an iommu fault handler isn't installed

Make report_iommu_fault() return -ENOSYS whenever an iommu fault
handler isn't installed, so IOMMU drivers can then do their own
platform-specific default behavior if they wanted.

Fault handlers can still return -ENOSYS in case they want to elicit the
default behavior of the IOMMU drivers.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3a072596b1b2173d0bce804983d6124066a36107..bd2d4d2764ddf2cf54491d43a3c49f109ba638db 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -43,6 +43,12 @@ EXPORT_SYMBOL_GPL(iommu_found);
  * iommu_set_fault_handler() - set a fault handler for an iommu domain
  * @domain: iommu domain
  * @handler: fault handler
+ *
+ * This function should be used by IOMMU users which want to be notified
+ * whenever an IOMMU fault happens.
+ *
+ * The fault handler itself should return 0 on success, and an appropriate
+ * error code otherwise.
  */
 void iommu_set_fault_handler(struct iommu_domain *domain,
                                        iommu_fault_handler_t handler)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index d084e8777e0ef629b4ef2de8830f0a0d8a90c239..ddad0ae0a43354451352803f0175c429ad663676 100644 (file)
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -98,11 +98,15 @@ extern void iommu_set_fault_handler(struct iommu_domain *domain,
  * Returns 0 on success and an appropriate error code otherwise (if dynamic
  * PTE/TLB loading will one day be supported, implementations will be able
  * to tell whether it succeeded or not according to this return value).
+ *
+ * Specifically, -ENOSYS is returned if a fault handler isn't installed
+ * (though fault handlers can also return -ENOSYS, in case they want to
+ * elicit the default behavior of the IOMMU drivers).
  */
 static inline int report_iommu_fault(struct iommu_domain *domain,
                struct device *dev, unsigned long iova, int flags)
 {
-       int ret = 0;
+       int ret = -ENOSYS;
 
        /*
         * if upper layers showed interest and installed a fault handler,